In adult and pediatric neurosurgery, cerebrospinal fluid (CSF) shunts are commonly used to treat hydrocephalus, arachnoid cysts, benign intracranial hypertension (pseudotumor cerebri), and other neurosurgical conditions characterized by raised intracranial pressure (ICP). Shunt over-drainage of CSF occurs with frequency—some shunts more than others. These patients develop intracranial hypotension, presumably related to the siphoning of CSF from the head when the patient is upright. This condition is referred to as over-shunting.
Children and adults with over-shunting frequently experience headaches. In a recent retrospective clinical review, 23% of shunted patients had headaches that were thought by the neurosurgeon to be the result of over-shunting on the basis of their clinical pictures. In addition, there are patients with headaches resulting from intracranial hypotension, due to the escape or over-drainage of CSF as a result of a lumbar puncture (the so-called spinal tap headache), post-operative pseudomeningocele, and chronic CSF leakage (CSF ottorhea and rhinorrhea).
Over-shunting headaches are usually intermittent. They tend to come on later in the day; patients rarely awaken with headache. There is frequently a postural component: laying down helps the headache. The ventricles are usually small on MRI or CT scan. Intracranial pressure is low, as indicated by introducing a needle into the shunt (the so-called shunt tap). A need exists for a solution to over-shunting headaches in particular patients.